1. Prior Art
The Prior art is believed best exemplified by the following U.S. Pat. Nos.: Hannon 2,934,030 05/61, Hannon Re. 25,005 07/61, Rudershausen 3,279,826 10/66, Hannon 3,413,171 11/68, Hannon 3,417,497 12/68, Peters 3,457,661 07/69, Conner 3,566,521 03/71, Thomas 3,582,439 06/71, Thomas 3,614,839 10/71, Staats 3,684,635 08/72, Staats 3,836,414 09/74, Whitehead 4,097,279 06/78.
2. Field of the Invention
This invention relates to multi-ply laminae and to the use of such laminae as post-laminations for identification cards, credentials and the like.
Numerous cards have been proposed which are designed to identify their holders to others. Typical examples are credit cards provided by department stores, service stations and the like; driver's licenses; identification badges such as those used to identify plant, government or school personnel or students; passports, visas and many other uses. To be satisfactory for such use, it is important that the cards, etc. be of such a nature that they cannot be counterfeited or tampered with or successfully altered without destroying or defacing the card so as to render the tampering or alteration noticeable. Unfortunately, providing such a tell-tale feature has not been wholly accomplished. Typical laminated cards may be cut with a knife or razor blade or delaminated with a solvent after which indicia or photographs can be substituted and the card readhered or relaminated without detection.
Several proposals have been made in the art for a tell-tale or tamper-proof identification card, i.e. a card that is not susceptible to alteration without ready detection. Proposals suggested have included, for example, magnetic tapes or coatings laminated on the surface of the card with a particular code sequence; invisible ultra-violet screening agents which become visible under fluorescent light; printed grids disposed between two layers of thermoplastic bonding material bonded so that identifying indicia is encased within bonding material which becomes distorted and/or destroyed upon application of heat or solvent, etc. Many of these proposals are ineffective and others, although effective require special detection equipment and offer detectability at prohibitive expense.